Shoe cementing apparatus



Oct. 6, 1942. E. L. CRANDELL. 2,298,038

SHOE CEMENT ING APPARATUS oct' ,6, 1942- E. L CRANDELL.

SHOE CEMENTING APPARATUS Filed June 15, 1941 2 Sheets-Sheet 2 L T J 59 Patented Oct. 6, 1942 SHOE CEMENTING APPARATUS Ervin L. Crandell, Wellesley, Mass., assignor to Compo Shoe Machinery Corporation, Boston, Mass., a corporation of Delaware Application June 1/3, 1941, Serial No. 397,874

8 Claims.

This invention relates to electrostatic heating apparatus, and relates more particularly to apparatus utilizing high frequency electrostatic fields for producing heat in an adhesive used for the cementing of shoe parts.

This invention is a continuation-in-part of my copending application, Serial No. 391,293, flied May 1, 1941.

In said application, I disclosed interlaced electrodesl arranged in a row at one side of work surfaces with a free or capacity coupled electrode arranged parallel to the interlaced electrodes, on the opposite side of the work surfaces. A single ended vacuum tube oscillator was disclosed for supplying high frequency electric energy to interlaced electrodes and acted to establish a concentrated electrostatic field between the interlaced electrodes as source electrodes and the free electrode, which field heated an adhesive between the work surfaces which were pressed together.

The present invention provides push-pull types of oscillator circuits for connection to source electrodes arranged at a common side of work surfaces. A free electrode is preferably used at the opposite side of the work surfaces, and the free electrode may be grounded.

Among the advantages of the push-pull types of circuits used with such electrodes are that the voltage losses through the oscillator tubes are reduced when the push-pull tubes are used, stray capacity between the electrodes and other portions of the apparatus are reduced, and with the free electrode at ground potential, no burns can occur in shoes being cemented due to electrostatic fields radiated towards metal tacks in the shoes.

An object of the invention is to improve the quality of cemented shoes.

Another object of the invention is to eliminate stray capacity between an electrode utilized for the production of an electrostatic field, and adjacent metal objects.

This invention relates as does the one disclosed in said copending application, generally to the heating of a dielectric such as cement by energy derived from a high frequency electrostatic field as disclosed in the Pitman Patent No. 2,087,480, and is well adapted to the quantity production of shoes utilizing a conveyor system as disclosed generally by the Smith Patent No. 2,109,323.

The invention will now be described with reference to the drawings, of which:

Fig. 1 is a side elevation illustrating a shoe press in which electrodes connected according to this invention, may be used;

Fig. 2 is a plan view, with a portion of the cover removed, of the electrode pad of Flg. 1;

Fig. 3 is a diagrammatic view showing interlaced electrodes arranged in a row, with a grounded free electrode, the interlaced electrodes being connected according to this invention to push-pull vacuum tube oscillators;

Fig. 4 is a diagrammatic view similar to Fig. 3 except that the push-pull circuit is provided by a single ended tube;

Fig. 5 is a diagrammatic view similar to Fig. 3 except that the electrodes are shown in side elevation instead of in plan, and

Fig. 6 is a diagrammatic view illustrating two shoe circuits being connected in series with each other and to a push-pull type of oscillator.

The shoe press I0 of Fig. 1 includes the inflatable pad I I into which a fluid such as air may be introduced to apply pressure to a shoe assembly I2, as disclosed in detail in said Smith patent.

In sole cementing, it is the practice to roughen the bottom of the lasted shoe and the top of the outsole and to coat these parts with an adhesive such as is disclosed in said Pitman patent. Then the assembly is placed in a press which forces the coated parts together, following which heat may be generated in the adhesive by a high frequency electrostatic field produced as will be described.

The electrode element indicated generally by I3 includes the interlaced source electrodes I4 and I5 which may be enclosed between flexible leather sheets I6 and I1, the margins of which may be joined by cement or stitches.

The electrodes III are interconnected by a common iiexible conductor I8 and the electrodes I5 are interconnected by a common conductor I 9, these conductors being arranged as shown by Fig. l to be connected to the terminals 22 and 23 for connection to the oscillator circuits which will be described. The terminals 22 and 23 are supported from the press Ill by the insulators 20 and l 2 I respectively.

The electrode pad I3 is placed in the press I0 upon the iniiatable pad II and the shoe assembly I2 containing the last 34 is placed upon the electrode pad I3 after the adhesive has been applied as described. The shoe assembly contains an electrode 33 which may be a metal bottom on the last 34 or which may be an electrode built into the shoe as disclosed in my copending application, Serial No. 387,823.

With reference now to Figs. 3 and 5, the vacuum tube triodes have their plates or anodes connected to opposite ends of the tank coil 31.

The coil 31 has its center tapped at 38 and the center tap is connected to the positive side of a suitable high voltage source, and through the blocking condenser 39, to ground. The negative side of the high voltage source is connected at lil to the cathodes of the tubes 35 and 3S.

The electrodes Id are connected through the conductor i8 and the blocking condenser lit to the tap 2 adjacent one end of the coil 31. The electrodes l are connected through the conductor i9 and the blocking condenser J3 to the tap le adjacent the other end o the coil 31.

The tubes 35`and 31 may be made to oscillate at a frequency which may be megacycles through feed back through their internal electrode capacities, the high frequency oscillations being applied through the tank lcoil 31 and the blocking condensers 4I and i3 to the electrodes Id and i 5.

The free electrode 33 is at a neutral potential and electrostatic fields are developed between it and the electrodes ill during one half cycle and between it and the electrodes l5 during the next half cycle. The electrodes id and I5 are 180 apart in phase, the free electrode 33 being the common or return path for both sets of the source electrodes. There is no'voltage developed upon the free electrode 33 and therefore no stray electrostatic fields can develop between it and any metal objects such as heel plates, tacks, etc., which may be present in the shoe or attached to the last. In prior electrode arrangements, electrostatic elds were developed between the electrodes and such metal objects resulting in occasional arcing and burning of the shoes.

Then too since the internal capacities of the tubes 35 and 3S are connected electrically in series, their internal voltage losses are halved resulting in increased voltage at the tank coil.

Fig. 4 illustrates how a single vacuum tube oscillator 45 may be connected to the tank coil 31 for supplying radio frequency voltage 180 out of phase to the source electrodes I4 and I5. One end of the tank coil 31 is connected to the anode 46 of the tube while its other end is connected through the condenser 41. to one end of the grid coil 48. The other end of the grid coil 48 is connected to the grid 49 of the tube. The coil 48 is connected at'its mid-point through the bias resistor 5D to the mid-point of the transformer secondary 5I supplying lament voltage to the cathode 52, and to ground..

The free electrode 33 may be grounded to the press I0 through the contacts of the metal member 53 of the press, with the metallic lining 54 in the last, and the conducting pin 55 which is in contact with the lining 54, with the upper surface of the free electrode 33. However, if the free electrode is not grounded, it remains a neutral electrode with no voltage developed upon it so long as it is centered with respect to the electrodes I4 and l5.

Fig. 6 illustrates how two sets of electrodes of the opposed type disclosed in said Smith patent may be connected in a push-pull circuit to a single tank coil 31 and which may receive energy from vacuum tube triodes connected as in Fig. 3. The lower electrodes 56 and 51 are contained within the two adjacent presses 58 and 59 respectively. The electrode 56 is connected through the wiping contacts 60 and the condenser 43 to the tap 44 on the coil 31, and the similar electrode 51 isconnected through the wiping contacts BI and the condenser I to the tap 42 on the coil 31. The upper electrodes 62 and 63 which may be metal last bottoms are grounded to their respective presses as disclosed in Fig. 1 thereof.

The presses of Fig. 6 are arranged in a conveyor system as disclosed in my copending application, Serial No. 390,555. In operation Athe presses move past the oscillator station and two adjacent presses at a time receive energy directly from the oscillator station through the wiping contacts. The two load circuits taken separately are unbalanced but when connected as disclosed they form a part of a single balanced push-pull circuit, enabling one oscillator station simultaneously to handle two loads without detuning or other adverse eiects.

While several embodiments of the invention have been described for the purpose of illustration, it should be understood that the invention is not limited to the exact apparatus and arrangements of apparatus illustrated, as modications thereof may be suggested by those skilled in the art without departure from the essence of the invention.

What is claimed is:

' 1. Electrostatic heating apparatus comprising a pair of electrodes arranged substantially in edge to edge alignment; means forming a pushpull, high frequency, oscillator circuit; means connecting said electrodes to opposite sides of said circuit, and a free electrode spaced from said electrodes.

2. Electrostatic heating apparatus comprising a pair of electrodes arranged substantially in edge to edge alignment; means forming a push pull, high frequency, oscillator circuit; means connecting said electrodes to opposite sides of said circuit, and a free electrode spaced from and lying substantially parallel to, said electrodes.

3. Electrostatic heating apparatus comprising a plurality of interlaced electrodes arranged substantially in edge to edge alignment; means forming a push pull, high frequency, oscillator circuit, means connecting alternate of said electrodes to opposite sides of said circuit, and a free electrode spaced from said electrodes.

4. Electrostatic heating apparatus comprising a plurality of interlaced electrodes arranged substantially in edge to edge alignment; means forming a push pull, high frequency, oscillator circuit, means connecting alternate of said electrodes to opposite sides of said circuit, and a freeelectrode spaced from and lying substantially parallel to, said electrodes.

5. Shoe cementing apparatus comprising a press; means including a pair 'of members adapted to be moved towards each other for pressing shoe parts together; a pair of electrodes movable with one of said members, means forming a push pull, high frequency, oscillator circuit, means connecting said electrodes to opposite sides of said circuit, and a free electrode supported adjacent the other of said members.

6. Shoe cementing apparatus comprising a press; means including a pair of members adapted to be moved towards each other for pressing shoe parts together; a pair of electrodes arranged substantially in edge to edge alignment movable with one of said members, means forming a push pull, high frequency, oscillator circuit, means connecting said electrodes to opposite sides of said circuit, and a free electrode supported adjacent the other of said members.

'1. Shoe cementing apparatus comprising a press; means including a pair of members adapted to be moved towards each other for pressing shoe parts together; a pair of electrodes arranged press; means including a pair of members adaptmembers.

ed to be moved towards each other for pressing shoe parts together; a plurality of interlaced electrodes movable with one of said members, means forming a push pull, high frequency, oscillator circuit, means connecting alternate of said electrodes to opposite sides of said circuit, and a free electrode supported adjacent the other o! said ERVIN L. CRANDmL 

